Histone proteins are integral components of chromosomes. Post-translational modifications (PTMs), such as methylation, acetylation, phosphorylation and ubiquitination, of histone proteins serve as marks for recruiting regulatory machineries controlling gene regulation, DNA repair, replication and chromatin condensation (Kouzarides, 2007; Strahl and Allis, 2000). Each of the histone proteins H2A, H2B, H3, and H4 is extensively modified, particularly in the flexible N-terminal tail domains (Wyrick & Parra, 2009; Epub Jul. 14, 2008). Over 100 different PTMs of histone proteins have been identified (Bock et al., 2011).
Not surprisingly, antibodies to PTMs of histone proteins accordingly are central research reagents in studies of chromatin biology and molecular epigenetics. Locus specific investigations of histone tail PTMs in chromatin rely on the specific interactions of modified histone tails with antibodies (Bock et al., 2011).
Antibodies to PTMs of histone proteins enable key investigatory techniques. For example, chromatin immunoprecipitation (ChIP) is a powerful technique for investigating histone PTMs, in which an antibody specific to a histone PTM of interest is used as an affinity reagent to enrich nucleosomes containing the histone PTM. The combination of ChIP with DNA microarray and high-throughput sequencing technology (ChIP-chip and ChIP-seq, respectively) enables the genome-wide distribution of histone PTMs to be studied and assists in revealing critical relationships between histone PTMs and biological function (Park, 2009). In addition to enabling key investigatory techniques like ChIP, antibodies are central components of common, standard analyses in epigenetics, including immunostaining, immunoblot, and immunosorbent assays (Ebert et al., 2006; Santos-Rosa et al., 2002).
However, most currently available antibodies to PTMs of histone proteins are polyclonal, and the mixed quality and the lack of reproducibility of available lots are major impediments to obtaining reliable and reproducible data. Embodiments provided herein seek to overcome this and other drawbacks inherent in the prior art.